@AlejandorLazaro if you imply using a hash that's not O(n) algorithm; it's O(n.log(n))

First thing I would do is to analyze your code loops and make absolutely sure that you're running a O(n) algorithm. Walk through your code with an example on pen and paper and see if your solution really does only visit each element once. If you want to test your code somewhere else, I suggest using https://ideone.com as a good sandbox playground for your code.

Also, remember that Codewars is still growing and sometimes experiences submission problems. While rare, it may be an issue on their side. Just hang in there and try again! :)

You are supposed to provide correct output for empty plugboard (i. e. plugboard = Plugboard(), no arguments provided).